Methods, devices, and systems for creating localized haptic stimulations on a user

ABSTRACT

A method of creating localized haptic stimulations on a user includes a wearable device including a plurality of transducers that can each generate one or more waves that propagate away from the wearable device through a medium. The method includes activating two or more transducers of the plurality of transducers, selecting values for characteristics of waves to be generated by the two or more transducers based at least in part on a known impedance of the medium. The method further includes generating, by the two or more transducers, waves that constructively interfere at a target location to create a haptic stimulation on a user of the wearable device, the waves having the selected values.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/636,699, filed Feb. 28, 2018, entitled “Methods, Devices, and Systemsfor Creating Haptic Stimulations and Tracking Motion of a User;” U.S.Provisional Application No. 62/647,559, filed Mar. 23, 2018, entitled“Methods, Devices, and Systems for Determining Contact On a User of aVirtual Reality and/or Augmented Reality Device;” U.S. ProvisionalApplication No. 62/647,560, filed Mar. 23, 2018, entitled “Methods,Devices, and Systems for Projecting an Image Onto a User and DetectingTouch Gestures;” and U.S. Provisional Application No. 62/614,790, filedJan. 8, 2018, entitled “Methods, Devices, and Systems for CreatingLocalized Haptic Sensations on a User,” each of which is incorporated byreference herein in its entirety.

This application is related to U.S. Utility patent application Ser. No.16/241,890 entitled “Methods, Devices, and Systems for DeterminingContact On a User of a Virtual Reality and/or Augmented Reality Device,”filed Jan. 7, 2019, U.S. Utility patent application Ser. No. 16/241,893entitled “Methods, Devices, and Systems for Displaying a User Interfaceon a User and Detecting Touch Gestures,” filed Jan. 7, 2019, and U.S.Utility patent application Ser. No. 16/241,871 entitled “Methods,Devices, and Systems for Creating Haptic Stimulations and TrackingMotion of a User,” filed Jan. 7, 2019, each of which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

This relates generally to haptic stimulation, including but not limitedto creating localized haptic stimulations on and providing hapticstimulation to a user of a virtual reality and/or augmented realitydevice.

BACKGROUND

Haptic or kinesthetic communication recreates the sense of touch byapplying forces, vibrations, and/or motions to a user. Mechanicallystimulating the skin may elicit long range responses, including wavesthat travel throughout a limb. The skin's/flesh's viscoelasticity yieldsfrequency-dependent attenuation and dispersion. Such stimulation of theskin/flesh elicits traveling waves that can reach far distances,affecting tactile localization and perception. However, creating astimulation of sufficient magnitude presents a challenge.

SUMMARY

Accordingly, there is a need for methods, devices, and systems forcreating localized stimulations having sufficient magnitudes. Onesolution is to generate multiple waves (e.g., ultrasonic waves) thatconstructively interfere at a target location. The constructiveinterference of the waves causes a haptic stimulation felt by a user.Additionally, time reversed focusing methods can be used for synthesisof waves for simulated contact at target locations on the user's body.

In some embodiments, the solution explained above can be implemented ona wearable device that includes a plurality of transducers (e.g.,actuators). The wearable device in some instances is worn on the user'swrist (or various other body parts) and is used to stimulate areas ofthe body outside of the wearable device's immediate area of contact.Moreover, the wearable device can be in communication with a host system(e.g., a virtual reality device and/or an augmented reality device,among others), and the wearable device can stimulate the body based oninstructions from the host system. As an example, the host system maydisplay media content (e.g., video data) or provide concomitant audiosignals to a user (e.g., the host system may instruct a head-mounteddisplay to display the video data), and the host system may alsoinstruct the wearable device to create localized haptic stimulationsthat correspond to the images displayed to the user. The media contentor the concomitant audio signals displayed by the host system could beused to modify the perceptual or cognitive interpretation of thestimulation (i.e. by displacing the perceived location of thestimulation towards a seen contact with an object, or by modifying theperceived pattern of vibration to be closer to the produced sound).

The devices, systems, and methods describes herein provide benefitsincluding but not limited to: (i) stimulating areas of the body outsideof the wearable device's immediate area of contact, (ii) creating hapticstimulations of varying magnitudes depending on visual data or otherdata gathered by sensors (e.g., sensors on the wearable device), (iii)the wearable device does not encumber free motion of a user's handand/or wrist (or other body parts), and (iv) multiple wearable devicescan be used simultaneously.

(A1) In accordance with some embodiments, a method is performed at awearable device that includes a plurality of transducers (or a singletransducer), where each transducer generates one or more waves (alsoreferred to herein as “signals”) that propagate away from the wearabledevice through a medium (e.g., through a sublayer of the user's skin,the user's flesh, the user's bone, etc.). The method includes activatingtwo or more transducers of the plurality of transducers. The methodfurther includes selecting values for characteristics of waves to begenerated by the two or more transducers based (or the singletransducer), at least in part, on a known impedance of the medium. Themethod further includes generating, by the two or more transducers,waves that constructively interfere at a target location to create ahaptic stimulation on a user of the wearable device, the waves havingthe selected values. In some embodiments, the waves are mechanical waves(e.g., soundwaves, ultrasonic waves, etc.). In some embodiments, thewearable device is attached to an appendage (e.g., wrist, forearm,bicep, thigh, ankle, chest, etc.) of the user. In some embodiments, thetarget location is on the appendage. For example, the wearable devicecan be attached to a wrist of the user with the target location being onthe user's hand attached to the wrist. In some embodiments, the targetlocation is on a finger, forearm, ankle, calf, bicep, ribs, etc. of theuser.

(A2) In some embodiments of the method of A1, generating the waves bythe two or more transducers includes transmitting the waves into a wristof the user in a first direction and the waves propagate through theuser's body away from the wrist in a second direction and constructivelyinterfere at the target location. In some embodiments, the firstdirection is substantially perpendicular to the second direction.

(A3) In some embodiments of the method of any of A1-A2, activating thetwo or more transducers includes: (i) activating a first transducer ofthe two or more transducers at a first time, and (ii) activating asecond transducer of the two or more transducers at a second time afterthe first time.

(A4) In some embodiments of the method of any of A1-A2, activating thetwo or more transducers includes activating the two or more transducerssimultaneously.

(A5) In some embodiments of the method of any of A1-A4, furtherincluding receiving an instruction from a host in communication with thewearable device. Activating the two or more transducers is performed inresponse to receiving the instruction from the host.

(A6) In some embodiments of the method of A5, the instruction receivedfrom the host identifies the target location.

(A7) In some embodiments of the method of any of A5-A6, the wearabledevice further includes a communication radio in wireless communicationwith the host, and the communication radio receives the instruction fromthe host.

(A8) In some embodiments of the method of any of A1-A7, the wearabledevice further includes a controller in communication with the pluralityof transducers, and the controller performs the activating and theselecting.

(A9) In some embodiments of the method of any of A1-A8, furtherincluding, at a second wearable device comprising a second plurality oftransducers that can each generate one or more waves that propagate awayfrom the second wearable device through the medium: (i) activating twoor more transducers of the second plurality of transducers, (ii)selecting second values for characteristics of waves generated by thetwo or more transducers of the second plurality of transducers based, atleast in part, on the known impedance of the medium, and (iii)generating, by the two or more transducers of the second plurality oftransducers, waves that constructively interfere at a different targetlocation to create a second haptic stimulation on the user, the waveshaving the second selected values.

(A10) In some embodiments of the method of A9, (i) the medium associatedwith the first wearable device is a first medium, and (ii) the mediumassociated with the second wearable device is a second medium having adifferent known impedance from the known impedance of the first medium.

(A11) In some embodiments of the method of A10, the second selectedvalues differ from the first selected values based on impedancedifferences between the first and second media.

(A12) In some embodiments of the method of any of A1-A11, the targetlocation is separated from the wearable device by a distance (e.g., anon-zero distance).

(A13) In some embodiments of the method of any of A1-A12, the wearabledevice further comprises a band to be secured around a wrist of theuser, and each of the plurality of transducers is coupled to the band.

(A14) In some embodiments of the method of A13, transducers of theplurality of transducers are radially spaced along a perimeter of theband.

(A15) In some embodiments of the method of any of A13-A14, the two ormore transducers are separated from one another by at least one othertransducer.

(A16) In some embodiments of the method of any of A13-A14, the two ormore transducers are adjacent to one another on the wearable device.

(A17) In some embodiments of the method of any of A1-A16, transducers ofthe plurality of transducers are spaced equidistant from one another onthe wearable device.

(A18) In some embodiments of the method of any of A1-A17, the pluralityof transducers is a first plurality of transducers, and the wearabledevice further comprises a second plurality of transducers.

In accordance with some embodiments, a wearable device includes one ormore processors/cores and memory storing one or more programs configuredto be executed by the one or more processors/cores. The one or moreprograms include instructions for performing the operations of themethod described above (A1-A18). In accordance with some embodiments, anon-transitory computer-readable storage medium has stored thereininstructions that, when executed by one or more processors/cores of awearable device, cause the wearable device to perform the operations ofthe method described above (A1-A18). In accordance with someembodiments, a system includes a wearable device, a head-mounted display(HMD), and a computer system to provide video/audio feed to the HMD andinstructions to the wearable device.

In another aspect, a wearable device is provided and the wearable deviceincludes means for performing any of the methods described herein(A1-A18).

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the various described embodiments,reference should be made to the Description of Embodiments below, inconjunction with the following drawings in which like reference numeralsrefer to corresponding parts throughout the figures and specification.

FIG. 1 is a block diagram illustrating an exemplary haptics system, inaccordance with various embodiments.

FIG. 2 is a block diagram illustrating an exemplary wearable device inaccordance with some embodiments.

FIG. 3 is a block diagram illustrating an exemplary computer system inaccordance with some embodiments.

FIG. 4 is an exemplary view of a wearable device on a user's wrist, inaccordance with some embodiments.

FIG. 5 is an exemplary cross-sectional view of a wearable device on theuser's wrist in accordance with some embodiments.

FIGS. 6A-6B are exemplary views of a wearable device in accordance withsome embodiments.

FIGS. 7A-7B are cross-sectional views of the wearable device of FIG. 6Ain accordance with some embodiments.

FIG. 8 illustrates the wearable device of FIG. 6A attached to a user'swrist in accordance with some embodiments.

FIGS. 9A-9B are a different views of the wearable device of FIG. 6Agenerating waves in accordance with some embodiments.

FIG. 10 is a flow diagram illustrating a method of creating localizedhaptic stimulations in accordance with some embodiments.

FIG. 11 is a flow diagram illustrating a method of managing creation oflocalized haptic stimulations in accordance with some embodiments.

FIG. 12 illustrates multiple crawling waves constructively interferingwith one another.

FIG. 13 illustrates an embodiment of an artificial reality device.

FIG. 14 illustrates an embodiment of an augmented reality headset and acorresponding neckband.

FIG. 15 illustrates an embodiment of a virtual reality headset.

DESCRIPTION OF EMBODIMENTS

Reference will now be made to embodiments, examples of which areillustrated in the accompanying drawings. In the following description,numerous specific details are set forth in order to provide anunderstanding of the various described embodiments. However, it will beapparent to one of ordinary skill in the art that the various describedembodiments may be practiced without these specific details. In otherinstances, well-known methods, procedures, components, circuits, andnetworks have not been described in detail so as not to unnecessarilyobscure aspects of the embodiments.

It will also be understood that, although the terms first, second, etc.are, in some instances, used herein to describe various elements, theseelements should not be limited by these terms. These terms are used onlyto distinguish one element from another. For example, a first wearabledevice could be termed a second wearable device, and, similarly, asecond wearable device could be termed a first wearable device, withoutdeparting from the scope of the various described embodiments. The firstwearable device and the second wearable device are both wearabledevices, but they are not the same wearable devices, unless specifiedotherwise.

The terminology used in the description of the various describedembodiments herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used in thedescription of the various described embodiments and the appendedclaims, the singular forms “a,” “an,” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will also be understood that the term “and/or” as usedherein refers to and encompasses any and all possible combinations ofone or more of the associated listed items. It will be furtherunderstood that the terms “includes,” “including,” “comprises,” and/or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps, operations, elements, components,and/or groups thereof.

As used herein, the term “if” is, optionally, construed to mean “when”or “upon” or “in response to determining” or “in response to detecting”or “in accordance with a determination that,” depending on the context.Similarly, the phrase “if it is determined” or “if [a stated conditionor event] is detected” is, optionally, construed to mean “upondetermining” or “in response to determining” or “upon detecting [thestated condition or event]” or “in response to detecting [the statedcondition or event]” or “in accordance with a determination that [astated condition or event] is detected,” depending on the context.

As used herein, the term “exemplary” is used in the sense of “serving asan example, instance, or illustration” and not in the sense of“representing the best of its kind.”

FIG. 1 is a block diagram illustrating a system 100, in accordance withvarious embodiments. While some example features are illustrated,various other features have not been illustrated for the sake of brevityand so as not to obscure pertinent aspects of the example embodimentsdisclosed herein. To that end, as a non-limiting example, the system 100includes a wearable device 102, which is used in conjunction with acomputer system 130 (e.g., a host system or a host computer). In someembodiments, the system 100 provides the functionality of a virtualreality device with haptics feedback, an augmented reality device withhaptics feedback, a combination thereof, or provides some otherfunctionality. The system 100 is described in greater detail below withreference FIGS. 13-15.

An example wearable device 102 (e.g., wearable device 102 a) includes,for example, one or more processors/cores 104 (referred to henceforth as“processors”), a memory 106, one or more transducer arrays 110, one ormore communications components 112, and/or one or more sensors 114. Insome embodiments, these components are interconnected by way of acommunications bus 108. References to these components of the wearabledevice 102 cover embodiments in which one or more of these components(and combinations thereof) are included. In some embodiments, the one ormore sensors 114 are part of the one or more transducer arrays 110(e.g., transducers in the transducer arrays 110 also perform thefunctions of the one or more sensors 114, discussed in further detailbelow). For example, one or more transducers in the transducer array 110may be electroacoustic transducers configured to detect acoustic waves(e.g., ultrasonic waves).

In some embodiments, a single processor 104 (e.g., processor 104 of thewearable device 102 a) executes software modules for controllingmultiple wearable devices 102 (e.g., wearable devices 102 b . . . 102n). In some embodiments, a single wearable device 102 (e.g., wearabledevice 102 a) includes multiple processors 104, such as one or morewearable device processors (configured to, e.g., control transmission ofwaves 116 by the transducer array 110), one or more communicationscomponent processors (configured to, e.g., control communicationstransmitted by communications component 112 and/or receivecommunications by way of communications component 112) and/or one ormore sensor processors (configured to, e.g., control operation of sensor114 and/or receive output from sensor 114).

The wearable device 102 is configured to generate (and receive) waves116 (signals) via the transducer array(s) 110. In particular, thewearable device 102 is configured to generate waves 116 that stimulateareas of the wearer's body outside of (i.e., away from) the wearabledevice's immediate area of contact (although in some instances thegenerated waves can also stimulate areas of the wearer below (e.g., at)the wearable device's immediate area of contact). In some embodiments,the transducers in a respective transducer array 110 are miniaturepiezoelectric actuators/devices, vibrotactile actuators, or the like. Insome embodiments, the transducers in a respective transducer array 110are single or multipole voice coil motors, or the like. The transducerarray(s) 110 are configured to generate and transmit waves 116 inresponse to being activated by the wearable device (e.g., via processors104 or some other controller included in the wearable device 102). Insome embodiments, the waves 116 are mechanical waves (e.g., sound waves,ultrasonic waves, or various other mechanical waves). A mechanical waveis an oscillation of matter, which transfers energy through a medium. Asdiscussed herein, the “medium” is the wearer's skin, flesh, bone, bloodvessels, etc. Due to an arrangement of the wearable device 102 (e.g., asshown in FIGS. 9A-9B), a wave 116 transmitted by a respective transducerin the array 110 creates oscillations or vibrations that areperpendicular to a direction of transmission. For example, if the wave116 is transmitted along the Y-axis from the respective transducer inthe array 110 (i.e., perpendicular to the medium, i.e., wearer'sskin/flesh/bone), the resulting oscillations or vibrations travel alongthe medium in the X-axis and/or Z-axis (at least initially). In someinstances, the resulting oscillations or vibrations are similar toripples created when a stone impacts a body of water. In otherinstances, the resulting vibrations resemble the transmitted waves 116a, 116 b (FIGS. 9A-9B), in that the transmitted wave 116 in essenceturns 90 degrees upon impacting the wearer's body.

In some embodiments, the wearable device 102 adjusts one or morecharacteristics (e.g., waveform characteristics, such as phase, gain,direction, amplitude, and/or frequency) of waves 116 based on a varietyof factors. For example, the wearable device 102 may select values ofcharacteristics for transmitting the waves 116 to account forcharacteristics of a user of the wearable device. In some embodiments,the wearable device 102 adjusts one or more characteristics of the waves116 such that the waves 116 converge at a predetermined location (e.g.,a target location), resulting in a controlled constructive interferencepattern. A haptic stimulation is felt by a wearer of the wearable deviceat the target location as a result of the controlled constructiveinterference pattern. In some embodiments, the wearable device 102creates or adjusts one or more characteristics of the waves 116 inresponse to the user movements. Selecting values of characteristics forthe waves 116 is discussed in further detail below with reference toFIG. 10.

Constructive interference of waves occurs when two or more waves 116 arein phase with each other and converge into a combined wave such that anamplitude of the combined wave is greater than amplitude of a single oneof the waves. For example, the positive and negative peaks of sinusoidalwaveforms arriving at a location from multiple transducers “addtogether” to create larger positive and negative peaks. In someembodiments, a haptic stimulation is felt (or a greatest amount is felt)by a user at a location where constructive interference of waves occurs(i.e., at the target location). Thus, to create a more intense hapticstimulation, a greater number of transducers may be activated, wherebymore waves “add together.” It is noted that user's may also feel thewaves travelling through the medium to the target location; however,these haptic stimulations will be less noticeable relative to the hapticstimulation created and felt at the target location.

As one example, two transducers of the wearable device 102 can producewaves (i.e., vibrations) that have respective frequencies of, say,10,000,000 and 10,000,010 Hz. In such a circumstance, the user wouldfeel 10 Hz (i.e., would feel the beat frequency) even though theproduced waves have respective frequencies of 10,000,000 and 10,000,010Hz. In another example, if a single transducer produces a wave with afrequency of 10,000,000 Hz, but the amplitude of the wave is modulatedat 10 Hz (e.g., amplitude modulation, AM), the user will feel the 10 Hz.Using this concept, multiple waves modulated at 10 Hz can be focused(i.e., constructively interfere) at a target location by using multipletransducers with waves out of phase, or by having the AM from thetransducers out of phase.

As will be discussed in greater detail below, the haptic stimulationcreated by the wearable device 102 can correspond to visual datadisplayed by the head-mounted display 140. To provide some context, thevisual data displayed by the head-mounted display 140 may depict aninsect crawling across the wearer's hand. The wearable device 102 maycreate one or more haptic stimulation(s) to mimic, but not necessarilymatch, a feeling of the insect crawling across the wearer's hand. As onecan imagine, an insect crawling across one's hand is a subtle feeling,and therefore the haptic stimulation(s) created by the wearable devicewould be similarly subtle. Further, as the insect moves across thewearer's hand, so would a location (or locations) of the hapticstimulation(s). As another example, the visual data displayed by thehead-mounted display 140 may depict the wearer catching an object (e.g.,a baseball). The wearable device 102 may create one or more hapticstimulations to induce the feeling of the object being caught by thewearer's hand (e.g., an impact of a baseball being caught issubstantial, and therefore the haptic stimulations created by thewearable device 102 would be equally substantial). In yet anotherexample, the visual data displayed by the head-mounted display 140 maydepict a user in a dark cave, and therefore the user's visual sense inessence cannot be used. In such an example, the wearable device 102 maycreate one or more haptic stimulations to mimic sensations encounteredin a cave, e.g., feeling of water dripping on the user, and/or batsflying past the user's arms, legs, and other body parts depending on thenumber of wearable devices 102 implemented.

In doing so, the wearer is further immersed into the virtual and/oraugmented reality such that the wearer not only sees the insect crawlingacross his or her hand, but also the wearer “feels” the insect crawlingacross his or her hand. Moreover, the wearable device is designed to notrestrict movement of the wearer's hand, as was the case with someprevious haptic stimulating device. For example, as shown in FIG. 8, thewearable device 600 is attached to a wrist of the user and therefore theuser's hand is unencumbered.

It is noted that the haptic stimulation created by the wearable device102 can correspond to additional data or events (i.e., not limited tovisual data displayed by the head-mounted display 140). For example, thehaptic stimulation created by the wearable device 102 can correspond tophysiological information of the wearer. The physiological informationmay be gathered by sensors 114 of the wearable device 102 (e.g., IMU,heart rate sensor, etc.) and/or sensors of other devices (e.g., sensors145 and cameras 139). The haptic stimulation may also correspond toproprioceptive events, such as mechanical stimulations produced by theuser (e.g., when the wearer taps on a virtual object). Information formechanical stimulations can also be gathered by sensors 114 of thewearable device 102 and/or sensors of other devices (e.g., sensors 145and cameras 139).

The computer system 130 is a computing device that executes virtualreality applications and/or augmented reality applications to processinput data from the sensors 145 on the head-mounted display 140 and thesensors 114 on the wearable device 102. The computer system 130 providesoutput data for (i) the electronic display 144 on the head-mounteddisplay 140 and (ii) the wearable device 102 (e.g., processors 104 ofthe haptic device 102, FIG. 2A). An exemplary computer system 130, forexample, includes one or more processor(s)/core(s) 132, a memory 134,one or more communications components 136, and/or one or more cameras139. In some embodiments, these components are interconnected by way ofa communications bus 138. References to these components of the computersystem 130 cover embodiments in which one or more of these components(and combinations thereof) are included.

In some embodiments, the computer system 130 is a standalone device thatis coupled to a head-mounted display 140. For example, the computersystem 130 has processor(s)/core(s) 132 for controlling one or morefunctions of the computer system 130 and the head-mounted display 140has processor(s)/core(s) 141 for controlling one or more functions ofthe head-mounted display 140. Alternatively, in some embodiments, thehead-mounted display 140 is a component of computer system 130. Forexample, the processor(s) 132 controls functions of the computer system130 and the head-mounted display 140. In addition, in some embodiments,the head-mounted display 140 includes the processor(s) 141 whichcommunicate with the processor(s) 132 of the computer system 130. Insome embodiments, communications between the computer system 130 and thehead-mounted display 140 occur via a wired connection betweencommunications bus 138 and communications bus 146. In some embodiments,the computer system 130 and the head-mounted display 140 share a singlecommunications bus. It is noted that in some instances the head-mounteddisplay 140 is separate from the computer system 130 (not shown).

The computer system 130 may be any suitable computer device, such as alaptop computer, a tablet device, a netbook, a personal digitalassistant, a mobile phone, a smart phone, a virtual reality device(e.g., a virtual reality (VR) device, an augmented reality (AR) device,or the like), a gaming device, a computer server, or any other computingdevice. The computer system 130 is sometimes called a host or a hostsystem. In some embodiments, the computer system 130 includes other userinterface components such as a keyboard, a touch-screen display, amouse, a track-pad, and/or any number of supplemental I/O devices to addfunctionality to computer system 130.

In some embodiments, the one or more cameras 139 of the computer system130 are used to facilitate virtual reality and/or augmented reality.Moreover, in some embodiments, the one or more cameras 139 also act asprojectors to display the virtual and/or augmented images (or in someembodiments the computer system includes one or more distinctprojectors). In some embodiments, the computer system 130 providesimages captured by the one or more cameras 139 to the display 144 of thehead-mounted display 140, and the display 144 in turn displays theprovided images. In some embodiments, the processors 141 of thehead-mounted display 140 process the provided images. It is noted thatin some embodiments the one or more cameras 139 are part of thehead-mounted display 140.

The head-mounted display 140 presents media to a user. Examples of mediapresented by the head-mounted display 140 include images, video, audio,or some combination thereof. In some embodiments, audio is presented viaan external device (e.g., speakers and/or headphones) that receivesaudio information from the head-mounted display 140, the computer system130, or both, and presents audio data based on the audio information. Anexemplary head-mounted display 140, for example, includes one or moreprocessor(s)/core(s) 141, a memory 142, and/or one or more displays 144.In some embodiments, these components are interconnected by way of acommunications bus 146. References to these components of thehead-mounted display 140 cover embodiments in which one or more of thesecomponents (and combinations thereof) are included. It is noted that insome embodiments the head-mounted display 140 includes one or moresensors 145. Alternatively, in some embodiments, the one or more sensors145 are part of the host system 130. FIGS. 14 and 15 illustrateadditional examples (e.g., AR system 1400 and VR system 1500) of thehead-mounted display 140.

The electronic display 144 displays images to the user in accordancewith data received from the computer system 130. In various embodiments,the electronic display 144 may comprise a single electronic display ormultiple electronic displays (e.g., one display for each eye of a user).The displayed images may be in virtual reality, augment reality, ormixed reality.

The optional sensors 145 include one or more hardware devices thatdetect spatial and motion information about the head-mounted display140. Spatial and motion information can include information about theposition, orientation, velocity, rotation, and acceleration of thehead-mounted display 140. For example, the sensors 145 may include oneor more inertial measurement units (IMUs) that detect rotation of theuser's head while the user is wearing the head-mounted display 140. Thisrotation information can then be used (e.g., by the computer system 130)to adjust the images displayed on the electronic display 144. In someembodiments, each IMU includes one or more gyroscopes, accelerometers,and/or magnetometers to collect the spatial and motion information. Insome embodiments, the sensors 145 include one or more cameras positionedon the head-mounted display 140.

In some embodiments, the transducer array 110 of the wearable device 102may include one or more transducers configured to generate the waves 116into a user of the wearable device, as discussed above (in someembodiments, the transducers also sense the transmitted waves).Integrated circuits (not shown) of the wearable device 102, such as acontroller circuit and/or waveform generator, may control the behaviorof the transducers (e.g., controller 412, FIG. 4). For example, based onthe information received from the computer system 130 by way of acommunication signal 118 (e.g., an instruction), a controller circuitmay select values of waveform characteristics (e.g., amplitude,frequency, trajectory, direction, phase, among other characteristics)used for generating the waves 116 that would provide a sufficient hapticstimulation at a target location on the user. The controller circuitfurther selects, at least in some embodiments, different values ofcharacteristics for transducers in the array 110 to effectively steerthe propagated waves to the target location. In this way, the controllercircuit is able to create constructive interference at the targetlocation. The controller circuit may also identify a subset oftransducers from the transducer array 110 that would be effective intransmitting the waves 116 and may in turn activate the identified set.

The communications component 112 includes a communications componentantenna for communicating with the computer system 130. Moreover, thecommunications component 136 includes a complementary communicationscomponent antenna that communicates with the communications component112. The respective communication components are discussed in furtherdetail below with reference to FIGS. 2 and 3.

In some embodiments, data contained within communication signals 118 isused by the wearable device 102 for selecting values for characteristicsused by the transducer array 110 to transmit the waves 116. In someembodiments, the data contained within the communication signals 118alerts the computer system 130 that the wearable device 102 is ready foruse. As will be described in more detail below, the computer system 130sends instructions to the wearable device 102, and in response toreceiving the instruction, the wearable device generates waves 116 thatcreate the haptic stimulation(s) on the wearer of the wearable device102.

In some embodiments, the wearable device 102 assigns a first task to afirst subset of transducers of the transducer array 110, a second taskto a second subset of transducers of the transducer array 110, and soon. The same transducer may be assigned to multiple subsets, includingboth the first and second subsets. In doing so, the different subsetsperform different tasks (e.g., creating a first haptic stimulation at afirst target location, creating a second haptic stimulation at a secondtarget location, and so on). Moreover, the first task may be assigned ata first point in time and the second task may be assigned at a secondpoint in time (or alternatively, the two tasks may be performedsimultaneously).

Non-limiting examples of sensors 114 and/or sensors 145 include, e.g.,infrared, pyroelectric, ultrasonic, laser, optical, Doppler, gyro,accelerometer, resonant LC sensors, capacitive sensors, heart ratesensors, acoustic sensors, and/or inductive sensors. In someembodiments, sensors 114 and/or sensors 145 are configured to gatherdata that is used to determine a hand posture of a user of the wearabledevice and/or an impedance of the medium. Examples of sensor data outputby these sensors include: body temperature data, infrared range-finderdata, motion data, activity recognition data, silhouette detection andrecognition data, gesture data, heart rate data, and other wearabledevice data (e.g., biometric readings and output, accelerometer data).In some embodiments, the transducers themselves serve as sensors.

FIG. 2 is a block diagram illustrating a representative wearable device102 in accordance with some embodiments. In some embodiments, thewearable device 102 includes one or more processing units (e.g., CPUs,microprocessors, and the like) 104, one or more communication components112, memory 106, one or more transducer arrays 110, and one or morecommunication buses 108 for interconnecting these components (sometimescalled a chipset). In some embodiments, the wearable device 102 includesone or more sensors 114 as described above with reference to FIG. 1. Insome embodiments (not shown), the wearable device 102 includes one ormore output devices such as one or more indicator lights, a sound card,a speaker, a small display for displaying textual information and errorcodes, etc.

Transducers in a respective transducer array 110 generate waves 116(FIG. 1). In some embodiments, the one or more transducers include,e.g., hardware capable of generating the waves 116 (e.g., soundwaves,ultrasound waves, etc.). For example, each transducer can convertelectrical signals into ultrasound waves. The one or more transducersmay be miniature piezoelectric transducers, capacitive transducers,single or multipole voice coil motors, and/or any other suitable devicefor creation of waves 116. The waves 116 may be standing waves.

In some embodiments, the one or more transducers are coupled with (orinclude) an oscillator and/or a frequency modulator that is used togenerate the waves so that the waves are appropriate for transmission.The oscillator and the frequency modulator may be part of an integratedcircuit included in the wearable device 102.

The communication component(s) 112 enable communication between thewearable device 102 and one or more communication networks. In someembodiments, the communication component(s) 112 include, e.g., hardwarecapable of data communications using any of a variety of wirelessprotocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee, 6LoWPAN, Thread, Z-Wave,Bluetooth Smart, ISA100.11a, WirelessHART, MiWi, etc.) wired protocols(e.g., Ethernet, HomePlug, etc.), and/or any other suitablecommunication protocol, including communication protocols not yetdeveloped as of the filing date of this document.

The memory 106 includes high-speed random access memory, such as DRAM,SRAM, DDR SRAM, or other random access solid state memory devices; and,optionally, includes non-volatile memory, such as one or more magneticdisk storage devices, one or more optical disk storage devices, one ormore flash memory devices, or one or more other non-volatile solid statestorage devices. The memory 106, or alternatively the non-volatilememory within memory 106, includes a non-transitory computer-readablestorage medium. In some embodiments, the memory 106, or thenon-transitory computer-readable storage medium of the memory 106,stores the following programs, modules, and data structures, or a subsetor superset thereof:

-   -   operating logic 216 including procedures for handling various        basic system services and for performing hardware dependent        tasks;    -   communication module 218 for coupling to and/or communicating        with remote devices (e.g., computer system 130, other wearable        devices, etc.) in conjunction with communication component(s)        112;    -   sensor module 220 for obtaining and processing sensor data        (e.g., in conjunction with sensor(s) 114 and/or transducer        arrays 110) to, for example, determine an orientation of the        wearable device 102 (among other purposes such as determining        hand pose of the user of the wearable device);    -   wave generating module 222 for generating and transmitting        (e.g., in conjunction with transducers(s) 110) waves, including        but not limited to creating a haptic stimulation at one or more        target locations). In some embodiments, the module 222 also        includes or is associated with a characteristic selection module        234 that is used to select values of characteristics for        generating the waves; and    -   database 224, including but not limited to:        -   sensor information 226 for storing and managing data            received, detected, and/or transmitted by one or more            sensors (e.g., sensors 114, one or more remote sensors,            and/or transducers);        -   device settings 228 for storing operational settings for the            wearable device 102 and/or one or more remote devices (e.g.,            selected values for characteristics of the waves);        -   communication protocol information 230 for storing and            managing protocol information for one or more protocols            (e.g., custom or standard wireless protocols, such as            ZigBee, Z-Wave, etc., and/or custom or standard wired            protocols, such as Ethernet); and        -   known impedances 232 for storing impedances for various            users of the wearable device.

In some embodiments, the characteristic selection module 234 of the wavegenerating module 222 may be used to select a particular frequency atwhich to transmit the waves. As discussed above, other characteristicsfor waves may include phase, gain, amplitude, direction, and theselection module 234 may select particular values for each of thosecharacteristics. In some embodiments, the selection module 234 selectsthe values based on information received from the computer system 130(as explained greater detail below). In some embodiments, the computersystem 130 includes the selection module 234 and provides the relevantcharacteristics to the wearable device 102.

In some embodiments (not shown), the wearable device 102 includes alocation detection device, such as a GNSS (e.g., GPS, GLONASS, etc.) orother geo-location receiver, for determining the location of thewearable device 102. Further, in some embodiments, the wearable device102 includes location detection module (e.g., a GPS, Wi-Fi, magnetic, orhybrid positioning module) for determining the location of the wearabledevice 102 (e.g., using the location detection device) and providingthis location information to the host system 130.

In some embodiments (not shown), the wearable device 102 includes aunique identifier stored in database 224. In some embodiments, thewearable device 102 sends the unique identifier to the host system 130to identify itself to the host system 130. This is particularly usefulwhen multiple wearable devices are being concurrently used.

In some embodiments, the wearable device 102 includes one or moreinertial measurement units (IMU) for detecting motion and/or a change inorientation of the wearable device 102. In some embodiments, thedetected motion and/or orientation of the wearable device 102 (e.g., themotion/change in orientation corresponding to movement of the user'shand) is used to manipulate an interface (or content within theinterface) displayed by the head-mounted display 140. In someembodiments, the IMU includes one or more gyroscopes, accelerometers,and/or magnetometers to collect IMU data. In some embodiments, the IMUmeasures motion and/or a change in orientation for multiple axes (e.g.,three axes, six axes, etc.). In such instances, the IMU may include oneor more instruments for each of the multiple axes. The one or more IMUsmay be part of the one or more sensors 114.

Each of the above-identified elements (e.g., modules stored in memory106 of the wearable device 102) is optionally stored in one or more ofthe previously mentioned memory devices, and corresponds to a set ofinstructions for performing the function(s) described above. The aboveidentified modules or programs (e.g., sets of instructions) need not beimplemented as separate software programs, procedures, or modules, andthus various subsets of these modules are optionally combined orotherwise rearranged in various embodiments. In some embodiments, thememory 106, optionally, stores a subset of the modules and datastructures identified above. Furthermore, the memory 106, optionally,stores additional modules and data structures not described above.

FIG. 3 is a block diagram illustrating a representative computer system130 in accordance with some embodiments. In some embodiments, thecomputer system 130 includes one or more processing units/cores (e.g.,CPUs, GPUs, microprocessors, and the like) 132, one or morecommunication components 136, memory 134, one or more cameras 139, andone or more communication buses 308 for interconnecting these components(sometimes called a chipset). In some embodiments, the computer system130 includes a head-mounted display interface 305 for connecting thecomputer system 130 with the head-mounted display 140. As discussedabove in FIG. 1, in some embodiments, the computer system 130 and thehead-mounted display 140 are together in a single device, whereas inother embodiments the computer system 130 and the head-mounted display140 are separate from one another.

Although not shown, in some embodiments, the computer system (and/or thehead-mounted display 140) includes one or more sensors 145 (as discussedabove with reference to FIG. 1).

The communication component(s) 136 enable communication between thecomputer system 130 and one or more communication networks. In someembodiments, the communication component(s) 136 include, e.g., hardwarecapable of data communications using any of a variety of custom orstandard wireless protocols (e.g., IEEE 802.15.4, Wi-Fi, ZigBee,6LoWPAN, Thread, Z-Wave, Bluetooth Smart, ISA100.11a, WirelessHART,MiWi, etc.) custom or standard wired protocols (e.g., Ethernet,HomePlug, etc.), and/or any other suitable communication protocol,including communication protocols not yet developed as of the filingdate of this document.

The memory 134 includes high-speed random access memory, such as DRAM,SRAM, DDR SRAM, or other random access solid state memory devices; and,optionally, includes non-volatile memory, such as one or more magneticdisk storage devices, one or more optical disk storage devices, one ormore flash memory devices, or one or more other non-volatile solid statestorage devices. The memory 134, or alternatively the non-volatilememory within memory 134, includes a non-transitory computer-readablestorage medium. In some embodiments, the memory 134, or thenon-transitory computer-readable storage medium of the memory 134,stores the following programs, modules, and data structures, or a subsetor superset thereof:

-   -   operating logic 316 including procedures for handling various        basic system services and for performing hardware dependent        tasks;    -   communication module 318 for coupling to and/or communicating        with remote devices (e.g., wearable devices 102 a-102-n, a        remote server (not shown), etc.) in conjunction with        communication component(s) 136;    -   virtual-reality generation module 320 that is used for        generating virtual-reality images and sending corresponding        video and audio data to the HMD 140 (in some embodiments, the        virtual-reality generation module 320 is an augmented-reality        generation module 320 (or the memory 134 includes a distinct        augmented-reality generation module) that is used for generating        augmented-reality images and projecting those images in        conjunction with the camera(s) 139 and the HMD 140);    -   instruction module 322 that is used for generating an        instruction that, when sent to the wearable device 102 (e.g.,        using the communications component 136), causes the wearable        device 102 to activate two or more transducers;    -   display module 324 that is used for displaying virtual-reality        images and/or augmented-reality images in conjunction with the        head-mounted display 140 and/or the camera(s) 139;    -   database 326, including but not limited to:        -   display information 328 for storing virtual-reality images            and/or augmented-reality images (e.g., visual data);        -   haptics information 330 for storing haptics information that            corresponds to the stored virtual-reality images and/or            augmented-reality images;        -   communication protocol information 332 for storing and            managing protocol information for one or more protocols            (e.g., custom or standard wireless protocols, such as            ZigBee, Z-Wave, etc., and/or custom or standard wired            protocols, such as Ethernet); and        -   mapping data 334 for storing and managing mapping data            (e.g., mapping one or more wearable devices 102 on a user).

In the example shown in FIG. 3, the computer system 130 further includesvirtual-reality (and/or augmented-reality) applications 336. In someembodiments, the virtual-reality applications 336 are implemented assoftware modules that are stored on the storage device and executed bythe processor. Each virtual-reality application 336 is a group ofinstructions that, when executed by a processor, generates virtualreality content for presentation to the user. A virtual-realityapplication 336 may generate virtual-reality content in response toinputs received from the user via movement of the head-mounted display140 or the wearable device 102. Examples of virtual-reality applications336 include gaming applications, conferencing applications, and videoplayback applications.

The virtual-reality generation module 320 is a software module thatallows virtual-reality applications 336 to operate in conjunction withthe head-mounted display 140 and the wearable device 102. Thevirtual-reality generation module 320 may receive information from thesensors 145 on the head-mounted display 140 and may, in turn provide theinformation to a virtual-reality application 336. Based on the receivedinformation, the virtual-reality generation module 320 determines mediacontent to provide to the head-mounted display 140 for presentation tothe user via the electronic display 144. For example, if thevirtual-reality generation module 320 receives information from thesensors 145 on the head-mounted display 140 indicating that the user haslooked to the left, the virtual-reality generation module 320 generatescontent for the head-mounted display 140 that mirrors the user'smovement in a virtual environment.

Similarly, in some embodiments, the virtual-reality generation module320 receives information from the sensors 114 on the wearable device 102and provides the information to a virtual-reality application 336. Theapplication 336 can use the information to perform an action within thevirtual world of the application 336. For example, if thevirtual-reality generation module 320 receives information from thesensors 114 that the user has raised his hand, a simulated hand (e.g.,the user's avatar) in the virtual-reality application 336 lifts to acorresponding height. As noted above, the information received by thevirtual-reality generation module 320 can also include information fromthe head-mounted display 140. For example, cameras 139 on thehead-mounted display 140 may capture movements of the user (e.g.,movement of the user's arm), and the application 336 can use thisadditional information to perform the action within the virtual world ofthe application 336.

To further illustrate with an augmented reality example, if theaugment-reality generation module 320 receives information from thesensors 114 that the user has rotated his forearm while, in augmentedreality, a user interface (e.g., a keypad) is displayed on the user'sforearm, the augmented-reality generation module 320 generates contentfor the head-mounted display 140 that mirrors the user's movement in theaugmented environment (e.g., the user interface rotates in accordancewith the rotation of the user's forearm).

Each of the above identified elements (e.g., modules stored in memory134 of the computer system 130) is optionally stored in one or more ofthe previously mentioned memory devices, and corresponds to a set ofinstructions for performing the function(s) described above. The aboveidentified modules or programs (e.g., sets of instructions) need not beimplemented as separate software programs, procedures, or modules, andthus various subsets of these modules are optionally combined orotherwise rearranged in various embodiments. In some embodiments, thememory 134, optionally, stores a subset of the modules and datastructures identified above.

FIG. 4 is an example view 400 of the wearable device 102 in accordancewith some embodiments. The view 400 shows the user's hand 408, user'swrist 404, user's arm 406, and the wearable device 102 on the user's arm406. Such an arrangement is merely one possible arrangement, and oneskilled in the art will appreciate that the discussion herein is notlimited to the arrangement shown in FIG. 4.

The wearable device 102 includes a wearable structure 402 that may be aflexible mechanical substrate such as a plastic (e.g., polyethylene orpolypropylene), rubber, nylon, synthetic, polymer, etc. In someembodiments, the wearable structure 402 is configured to be worn aroundat least a portion of a user's wrist or arm 404/406 (and various otherbody parts). The wearable device 102 includes a transducer array 110,including a plurality of transducers 410 arranged at different locationson the wearable structure 402. The transducers 410 can be arranged in apattern along an inner surface of the wearable structure 402 facing thearm 406 such that the transducers 410 contact the user's skin. Inanother example, the transducers can be arranged in a radial patternalong an inner perimeter of the wearable structure 602 (FIG. 6B).

Transducer 410 generates waves (e.g., waves 116, FIG. 1) in response toreceiving one or more control signals from a controller 412. The one ormore control signals instruct one or more transducers 410 in thetransducer array 110 to send waves (e.g., ultrasonic waves) into theuser's wrist or arm. In some embodiments, the wearable device 102includes one or more sensors (e.g., sensors 114, FIG. 1) mounted on thewearable structure 402 to measure impedance of the user's wrist or arm.In some embodiments, the wearable structure 402 includes a memory (e.g.,memory 106, FIG. 1) that stores known impedances of a user (or multipleusers), as discussed above. In some embodiments, the controller 412generates a control signal (or multiple signals) based on an instructionfrom a host system (e.g., computer system 130, FIG. 1). In someembodiments, the instruction from the host system is based oninformation received from one or more sensors of the wearable device 102(e.g., based on information from the optional IMU and/or informationfrom the sensors 114, such as a heart rate sensor). Alternatively or inaddition, the controller 412 may generate a control signal (or multiplesignals) based on information received from one or more sensors of thewearable device 102

The wearable device 102 is placed on a user's arm 406 to send hapticstimulation to the user. For example, haptic stimulation (e.g., tactilefeedback) includes a touch stimulation, a swipe stimulation, a pullstimulation, a push stimulation, a rotation stimulation, a heatstimulation, and/or a pain stimulation. In some embodiments, eachtransducer 410 on the wearable device 102 functions individually tocreate the haptic stimulation. Alternatively, in some embodiments, twoor more transducers function together to create the haptic stimulation.In some embodiments, less than all the transducers function to createthe haptic stimulation. For example, a first group of transducers (twoor more transducers) may function to create first haptic stimulation ata first location and a second group of transducers (two or moredifferent transducers) may function to create second haptic stimulationat a second location. In some embodiments, a threshold number oftransducers is needed to create the haptic stimulation. For example, twoor more transducers need to generate ultrasonic waves in order for thehaptic stimulation to be felt by a user of the wearable device. In someembodiments, a magnitude of the haptic stimulation felt by the userincreases as the number of transducers generating ultrasonic wavesincreases.

As discussed above, oscillations or vibrations travel along (e.g.,within) the wearer's body as a result of a wave 116 being generated by atransducer 410. The resulting oscillations or vibrations from the wave116 are sometimes referred to herein as crawling waves (the “crawlingwave phenomena”). In the present context, the crawling wave phenomenarefers to two or more sources (i.e., transducers) with differentharmonic/acoustic excitations that induce moving interference patternsin the wearer's body. The crawling wave generated by the sources movesthrough the wearer's body with a phase velocity (v) that depends on theharmonic frequencies (f1, f2), and the shear wave speed (s). In someembodiments, the following equation represents the phase velocity (v) ofa crawling wave:

$v = {{s\left( {{f\; 1} - {f\; 2}} \right)}/\sqrt{4\; f\; 1*f\; 2}}$

As an example, when f1=500 Hz, f2=501 Hz, s=5 m/s, a phase velocity ofv≈1 cm/s results. In some embodiments, values for the parameters of theequation above are provided by the computer system 130, or the valuesare calculated by the wearable device 102 based on an instruction fromthe computer system 130.

An example of multiple crawling waves constructively interfering withone another is illustrated in FIG. 12 (view B). As shown, the crawlingwaves constructively interfere at location 1202, which corresponds to ahaptic stimulation. In some embodiments, time reversal focusingtechniques are used to determine parameters of the crawling wavesillustrated in FIG. 12, as explained below. For example, the determinedparameters are used to create the haptic stimulation at location 1202(FIG. 12).

In some embodiments, the transducers 410 focus ultrasound waves into theuser using time reversal signal processing. In other words, the wearabledevice is a device that can focus waves using a time reversal method.Time reversal signal processing takes advantage of wave reciprocity,which is not altered by non-linear media, such as the user's skin. Tofocus the ultrasound waves using time reversal techniques, for each ofthe transducers 410, the wearable device activates the respectivetransducers (e.g., each transducer shown in FIG. 12) with a test signaland measures the response at the respective target location (e.g.,location 1202, FIG. 12). Various instruments can be used to measure theresponse at the respective target location, including but not limited toa laser Doppler vibrometer. Thereafter, the measured signals aretime-reversed. By activating the transducers 410 (e.g., all or less thanall) with time-reversed versions of the measured signals, an excitedskin (or other media) response can be created at the target location(e.g., the signals constructively interfere at the target location). Asone skilled in the art will appreciate, in some instances, theparameters of each crawling wave are the same, whereas in some otherinstances, the parameters of crawling waves differs. Moreover, a firsttransducer may be activated at a first time and a second transducer maybe activated at a second time (e.g., after the first time) (or in someembodiments, each transducer is activated simultaneously).

In some embodiments, the transducer array 110 includes transducers 410designed to make contact with human skin. A contact area having aconductive agent and padding may be used on the wearable device 102behind each transducer to improve subject comfort and reduce contactimpedances (e.g., as shown in FIG. 5). The conductive agent between thetransducer and skin may be a “wet” connection using a conductive gel,which may consist of propylene glycol and NaCl, or a “dry” connection,such as a thin layer of conductive polymer (e.g., carbon-doped PDMS).

FIG. 5 is an example cross section 500 of a wearable device inaccordance with some embodiments (taken along line X-Y, FIG. 4). Thecross sectional view 500 shows the wearable device 102 on a user's arm406, as described above in FIG. 4. As shown, each transducer generatesand transmits a wave 116 a-116 d (e.g., an ultrasonic wave) in theuser's arm 406. The conductive agent 502 reduces the impedance presentedto the waves 116 at the contact between the transducers 410 and the skinof the arm 406.

As shown, the transmitted waves 116 a-116 d extend into the user's body(e.g., extend into the epidermis, the dermis, the muscles, the tendons,the ligaments, the bones, etc.). In some circumstances, the impact ofthe transmitted waves 116 a-116 d causes crawling waves to radiate awayfrom the impact locations using the user's body as a medium (e.g., asshown in FIG. 12). Although the waves 116 a-116 d are shown travelling aminimal distance into the user's body, in some instances the waves 116a-116 d travel at least half way through the body (e.g., to the bone).

FIG. 6A is an isometric view of the wearable device 600 in accordancewith some embodiments. The wearable device 600 is an example of thewearable device 102. The wearable device 600 is configured to beattached to a part of a user's body. For example, the wearable device600 is configured to be attached to a wrist, forearm, ankle, bicep,calf, thigh, and various other parts of the user's body. In someembodiments, the wearable device 600 is a rigid or semi-rigid structure.Alternatively, in some embodiments, the wearable device 102 is aflexible structure. Although the wearable device 600 is shown as acontinuous circle, the wearable device 600 may break apart to beattached to the user's body (e.g., in a similar fashion to a watch).

FIG. 6B is a cross-sectional view of the wearable device 600 inaccordance with some embodiments. The wearable device 600 includes awearable structure 602. The wearable structure 602 wraps around the partof the user's body. The wearable device 600 further includes a pluralityof transducers 410 (FIG. 4) positioned along an inner perimeter of thewearable structure 602. The transducers 410 in this example are radiallyspaced, such that the transducers 410 wrap around the wearable structure602 and form a substantially contiguous circle of transducers. In suchan arrangement, the wearable device 600 is able to produce waves 116 ina 360-degree fashion. In some embodiments, the wearable structure 602separates the transducers 410 from the user's skin. Alternatively, insome embodiments (not shown), the transducers 410 are in direct contactwith the user's skin (a conductive agent may also be included, asdescribed above with reference to FIG. 5).

FIGS. 7A-7B are cross-sectional views of the wearable device 600 inaccordance with some embodiments. FIG. 7A illustrates a singlearrangement of transducers 410 along a length of the wearable structure602. FIG. 7B illustrates a double arrangement of transducers 410A, 410Balong the length of the wearable structure 602 (other arrangements arepossible, such as a triple arrangement). In some embodiments (notshown), the transducers are staggered such that transducers in a givenrow are not parallel, but are instead offset from one another.

FIG. 8 illustrates the wearable device 600 attached to a user's wrist.Left of the wearable device 600 is the user's arm 802 and right of thewearable device 600 is the user's hand 804. The wearable device 600could also be attached to a user's ankle, or various other body parts.

FIG. 9A is a cross-sectional view 900 of the wearable device 600 takenalong “A” view, in accordance with some embodiments. The user's arm hasbeen removed from FIG. 9A for ease of illustration. As shown, twotransducers 410A, 410B from the transducer array 110 are activated(indicated by shading), and each is generating a respective wave 116 a,116 b. In some embodiments, the wearable device 600 selectivelyactivates a subset of the transducer array 110 based at least in part ona desired target location. In this example, the target location 912 istowards an upper portion of the user's hand 804. Accordingly, thewearable device 600 selectively activates the two shaded transducers410A and 410B (it is noted that the displayed selection is merely usedfor illustrative purposes). In response to being activated, the twotransducers 410A and 110B each generates a wave 116 a, 116 b into theuser's body directly below the wearable device 102 (i.e., the generatedwaves 116 a, 116 b, at least initially, travel perpendicular to theuser's skin). As will be explained with reference to FIG. 9B, thegenerated waves end up travelling parallel to the user's body afterinitially travelling perpendicular to the user's body.

FIG. 9B is an example top view 902 that shows the wearable device 600and the user's arm taken along “B” view, in accordance with someembodiments. As shown, the two waves 116 a, 116 b generated by the twotransducers parallel the user's body and are using the arm as themedium. The two waves 116 a, 116 b, after initially travellingperpendicular to the user's arm, travel parallel to the user's bodyafter contacting and interacting with the user's body. The two waves 116a, 116 b propagate within a sublayer of the body away from an impactlocation. In some embodiments, a direction of the two waves 116 a, 116 bis different, such as normal to and tangential with the skin, which canlead to different conduction velocities and attenuation. For example,one of the waves may initially travel perpendicular to the user's armwhile another wave may initially travel parallel to the user's arm.

Values of characteristics of each wave are selected by the wearabledevice 600 (or the host system 130) so that the two waves 116 a, 116 bconstructively interfere at the target location 912. It is noted thatthe two waves 116 a, 116 b in FIG. 9B are shown as being substantiallysinusoidal in shape. However, in some instances, the two waves 116 a,116 b resemble ripples on a body of water (e.g., as shown in FIG. 12).For example, the first wave 116 a creates a first ripple that propagateswithin a sublayer of the body away from the impact location and thesecond wave 116 b creates a second ripple that propagates within asublayer of the body away from the impact location. Based on thecharacteristics of the ripples, the propagation medium, and a spacing ofthe two impact locations, the two waves 116 a, 116 b constructivelyinterfere at the target location 912.

As will be explained in more detail below with reference to FIG. 10,values for the characteristics of the waves are selected based at leastin part on characteristics of the user and the target location.

FIG. 10 is a flow diagram illustrating a method 1000 of creatinglocalized haptic stimulations on a user in accordance with someembodiments. The steps of the method 1000 may be performed by a wearabledevice (e.g., a wearable device 102, FIG. 1). FIG. 10 corresponds toinstructions stored in a computer memory or computer readable storagemedium (e.g., memory 106 of the wearable device 102). For example, theoperations of method 1000 are performed, at least in part, by acommunication module (e.g., communication module 218, FIG. 2), a wavegenerating module (e.g., wave generating module 222, FIG. 2), and/orcharacteristics selection module (e.g., characteristics selection module236, FIG. 2).

The method 1000 is performed at a wearable device that includes aplurality of transducers (e.g., transducer array 110, FIG. 1), whereeach transducer generates one or more waves (e.g., waves 116, FIG. 1)that propagate away from the wearable device through a medium. In someembodiments, the transducers are an array of miniature piezoelectricdevices. Alternatively or in addition, in some embodiments, thetransducers are an array of single or multipole voice coil motors. Insome embodiments, the one or more waves are mechanical waves, such asultrasonic waves, soundwaves, or the like. In some embodiments, the oneor more waves are electromagnetic waves, or various other waves. In someembodiments, the medium is skin (or flesh, bone, etc.) of a user wearingthe wearable device. For example, the wearable device may be attached toa wrist of the user, and the one or more waves may propagate away fromthe wearable device through the skin below the wearable device. In someembodiments, the plurality of transducers contacts the user's skin. Insome embodiments, the wearable device further includes a band (e.g.,wearable structure 402, FIG. 4; wearable structure 602, FIG. 6A) to besecured around a wrist (or other body part) of the user, and each of theplurality of transducers is coupled to (e.g., integrated with) the band.In some embodiments, the plurality of transducers is radially spacedalong a perimeter of the band (e.g., transducer arrangement shown inFIG. 6B). In some embodiments, the wearable device includes a housingthat houses the components of the wearable device.

The method 1000 includes activating (1004) two or more transducers of aplurality of transducers (e.g., transducers 410A and 410B, FIG. 9A). Insome embodiments, a controller (e.g., controller 412, FIG. 4) performsthe activating. In some embodiments, the controller is part of thewearable device. Alternatively, in some embodiments, the controller ispart of the host system 130 (FIG. 1). In some embodiments, activatingthe two or more transducers comprises activating the two or moretransducers simultaneously. Alternatively, in some embodiments,activating the two or more transducers comprises: (i) activating a firsttransducer of the two or more transducers at a first time and (ii)activating a second transducer of the two or more transducers at asecond time after the first time. For example, in some circumstances(e.g., depending on a target location and a position of each transduceron the wearable device), the two or more transducers are activated atdifferent times to ensure that the waves transmitted by the two or moretransducers constructively interfere with another at the targetlocation. In some embodiments, a time difference between each respectiveactivation increases based a distance between each transducer on thewearable device. In some embodiments, the time difference between eachrespective activation is further determined according to the selectedvalues for the characteristics of the waves (discussed below).

It is noted that, in some embodiments, the method 1000 includesactivating a single transducer. For example, instead of the wearabledevice including a plurality of transducers, the wearable device mayinclude one large transducer that is able to create multiple waves(e.g., the transducer has a shape of a lattice or a layer that can beactivated selectively at different locations). Such a circumstance mayarise when a magnitude of the haptic stimulation needs to be subtle(i.e., almost unnoticeable). Additionally, in some instances, the singletransducer is able to create haptic stimulations at various magnitudes(large and small). In such embodiments, the following steps in themethod 1000 may be performed by a single transducer.

The method 1000 further includes selecting (1006) values forcharacteristics of waves to be generated by the two or more transducersbased, at least in part, on a known impedance of the medium. In someinstances, the known impedance of the medium is determined based oncharacteristics of the user. The characteristics of the user include butare not limited to age, sex, body fat index, and area of the body. Forexample, a wrist of an older male user may have a first known impedanceand a calf of a younger female user may have a second known impedancedifferent from the first known impedance. In light of these differences,the selected values for the characteristics of the waves to be generatedfor the first known impedance may differ from the selected values forthe characteristics of the waves to be generated for the second knownimpedance. The characteristics of the waves include but are not limitedto frequency, amplitude, phase, wavelength, and gain. Moreover, in someembodiments, shapes of the waves include but are not limited to sine,triangle, square, asymmetric, and arbitrary. In some embodiments,selecting (1006) the values for the characteristics of the waves to begenerated by the two or more transducers is further based on a targetlocation and an arrangement of the transducer array 110 (e.g., accountfor differences between transducer array 110 (FIG. 4) and transducerarray 110 (FIG. 6B)).

In some embodiments, time reversal focusing techniques are used todetermine the values for the characteristics of the waves and a timeshift (as explained above with reference to FIG. 4).

The method 1000 further includes generating (1008), by the two or moretransducers, waves that constructively interfere at a target location tocreate a haptic stimulation on a user of the wearable device. The waveshave the selected values. In some embodiments, the haptic stimulation isselected from a group comprising a touch stimulation, a swipestimulation, a pull stimulation, a push stimulation, a rotationstimulation, a heat stimulation, and a pain stimulation. For example, afirst haptic stimulation may mimic a breath on the back of the user'shand (a subtle haptic stimulation) and a second haptic stimulation maymimic a flame on the palm of the user's hand (an intense hapticstimulation) (e.g., the wearer's character in a virtual-reality videogame is lighting a cigar). In some embodiments, the first hapticstimulation may mimic physiological states of the user. For example, ifthe wearer's character in a virtual-reality video game is running, thena haptic stimulation mimicking the wearer's heartbeat may be createdusing data from the sensors 114 of the wearable device 102 (e.g., theoptional IMU and/or the sensors 114, such as a heart rate sensor). Insome embodiments, the wearable device is positioned on the wearer'schest.

It is noted that the target location can be located on the wearer'sother arm/hand. For example, the wearable device 102 may be worn on thewearer's left hand, and the target location may be on the wearer's rightforearm. Accordingly, when the wearer's two arms come into contact(i.e., if the wearer touches his or her left forearm with his or herright index finger), the haptic stimulation may be created in the rightindex finger, which is then felt in the left forearm when contact ismade between the two body parts. Because of the different distributionof receptors in the arms and hands, it may be less complex to induce thepercept of a localized stimulation on a finger, rather than the forearm.

In some embodiments, the method 1000 further includes receiving aninstruction from a host (e.g., host system 130, FIG. 1) in communicationwith the wearable device. In some embodiments, the instruction from thehost is based on information received from one or more sensors of thewearable device 102 (e.g., based on information from the optional IMUand/or information from the sensors 114, such as a heart rate sensor).Alternatively or in addition, the instruction from the host is based oninformation received from one or more sensors of the head-mounteddisplay. Alternatively or in addition, the instruction from the host isbased on media content of an application (e.g., VR/AR applications 336,FIG. 3) executing at the host (e.g., visual and/or audio data of a gameor other program). Further, in some embodiments, activating the two ormore transducers is performed in response to receiving the instructionfrom the host. In some embodiments, the instruction received from thehost identifies the target location. In some embodiments, the targetlocation is separated from the wearable device by a distance. Forexample, the wearable device is attached to a wrist of the user, and thetarget location is on the hand of the user.

To further illustrate using the cigar example from above. The host maycommunicate visual data with a head-mounted display 140 (FIG. 1), wherethe visual data, when displayed by the head-mounted display, depicts thewearer's character in a virtual-reality video game lighting a cigar.Concurrently, the host may communicate an instruction to the wearabledevice, where the instruction, when performed by the wearable device,causes the wearable device to generate waves by the two or moretransducers that create a haptic stimulation that mimics the flamedisplayed by the head-mounted display 140. As one can imagine, in orderfor the haptic stimulation to be realistic, the haptic stimulationcoincides with the visual data displayed by the head-mounted display140. Moreover, because the wearable device is attached to the user'swrist, the user's hand remains unencumbered, which results in a morerealistic virtual reality (or augmented reality) experience for theuser.

Further, in those embodiments where the instruction is received from thehost, the wearable device includes a communication radio (e.g.,communications component 112, FIG. 1) in wireless communication with thehost. The communication radio receives the instructions from the host(e.g., via a communication signal 116, FIG. 1).

In some embodiments, generating the waves by the two or more transducerscomprises transmitting the waves into a wrist of the user in a firstdirection (or various other parts of the body depending on a location ofthe wearable device, e.g., ankle, bicep, etc.). In such embodiments, thewaves propagate through the user's body (e.g., skin, flesh, bone, bloodvessels, etc.) away from the wrist in a second direction andconstructively interfere at the target location. The first direction issubstantially perpendicular to the second direction. It is noted thateach wave propagating through the user's body may propagate in a uniquedirection that is different from the first direction, and the directionof other propagating waves.

In some embodiments, the two or more transducers are separated from oneanother by at least one other transducer. Alternatively, in someembodiments, the two or more transducers are adjacent to one another onthe wearable device. In some embodiments, the plurality of transducersis spaced equidistance from one another on the wearable device. In someembodiments, the two or more transducers include all the transducers inthe plurality of transducers.

In some embodiments, the plurality of transducers is a first pluralityof transducers and the wearable device further comprises a secondplurality of transducers. In some embodiments, the first plurality oftransducers generates waves at a first frequency, and the secondplurality of transducers generates waves at a second frequency distinctfrom the first frequency. In some embodiments, the first plurality oftransducers and the second plurality of transducers generate waves at asubstantially similar frequency. In some embodiments, the first andsecond pluralities of transducers are arranged in an array. Variousarrangements of transducers are discussed in further detail at FIGS.7A-7B.

In some embodiments, the waves are generated at a frequency rangebetween 30 and 300 Hz. It should be noted that greater (or lesser)frequencies can also be used, depending on the circumstances. In someembodiments, the waves are generated at a frequency range between 20 and20,000 Hz.

In some embodiments, the method 1000 further includes, at a secondwearable device (e.g., wearable device 102 b, FIG. 1) having a secondplurality of transducers that can each generate one or more waves thatpropagate away from the second wearable device through the medium,activating two or more transducers of the second plurality oftransducers. The second wearable device selects second values forcharacteristics of waves generated by the two or more transducers of thesecond plurality of transducers based, at least in part, on the knownimpedance of the medium. Further, the second wearable device generates,by the two or more transducers of the second plurality of transducers,waves that constructively interfere at a different target location tocreate a second haptic stimulation on the user. The waves have thesecond selected values.

For example, the first wearable device may be attached to a left wristof the user and the second wearable device may be attached to a rightwrist of the user. In another example (or in addition to the previousexample), the first wearable device may be attached to a left ankle ofthe user and the second wearable device may be attached to a right ankleof the user. As discussed above, the wearable devices may be attached tovarious body parts.

In some embodiments, the medium associated with the first wearabledevice is a first medium and the medium associated with the secondwearable device is a second medium having a different known impedancefrom the known impedance of the first medium. Accordingly, the secondselected values may differ from the first selected values based on theimpedance difference between the first and second media. In someembodiments, the known impedances 232 are stored in memory 106 of thewearable device(s) (FIG. 2). Alternatively or in addition, the knownimpedances are stored in memory 134 of the host system (FIG. 3) (notshown).

In some embodiments, the method 1000 includes activating one or moretransducers on the first wearable device and one or more transducers onthe second wearable device, instead of just activating transducers onthe first wearable device (or in addition to activating the two or moretransducers on the first wearable device).

FIG. 11 is a flow diagram illustrating a method 1100 of managingcreation of localized haptic stimulations in accordance with someembodiments. The steps of the method 1100 may be performed by a hostsystem (e.g., computer system 130, FIG. 1). FIG. 11 corresponds toinstructions stored in a computer memory or computer readable storagemedium (e.g., memory 134 of the computer system 130). For example, theoperations of method 1000 are performed, at least in part, by acommunication module (e.g., communication module 318, FIG. 3), avirtual-reality/augment reality generation module (e.g., virtual-realitygeneration module 320, FIG. 3), an instruction generation module (e.g.,instruction generation module 322, FIG. 3), and/or a display module(e.g., display module 324, FIG. 3). In some embodiments, the host systemcorresponds to the AR system 1400 and/or the VR system 1500.

It is noted that the steps of the method 1100 can be performed inconjunction with the steps the method 1000. The host system is incommunication with at least one wearable device (e.g., wearable device102 a, FIG. 1). However, in some embodiments, the host system is incommunication with multiple wearable devices, and the host system usesmapping data 334 to manage each wearable device (FIG. 3). It is notedthat the various wearable devices are not limited to particularappendage, and therefore, the host system updates the mapping data 334upon start-up of the system. To accomplish the updating, the wearabledevice(s) being used each send location information to the host system,and the host system updates the mapping data 334 based on the locationinformation. In this way, the host system can determine that a firstwearable device is attached to the left arm, even though the firstwearable device was attached to the right arm during a previous usage ofthe system. In some embodiments, each wearable device has an identifierthat allows the host system to differentiate between each wearabledevice (as described above with reference to FIG. 2). The identifier maybe included in the location information or may be sent separately.

The method 1100 includes generating (1104) an instruction thatcorresponds to visual data to be displayed by the host system. In someembodiments, the host system generates the instruction based oninformation received from the sensors 114 on the wearable device 102.Additionally, the information received by the host system can alsoinclude information from the head-mounted display 140. For example,cameras on the head-mounted display 140 may capture movements of thewearable device 102, and the host system can use this additionalinformation when generating the instruction.

The method 1100 further includes sending (1106) the instruction to thewearable device in communication with the host system (e.g., send theinstruction in a communication signal 118 from the communicationscomponent 136, FIG. 1). The instruction, when received by the wearabledevice, causes the wearable device to activate two or more transducersincluded in the wearable device.

After (or while) sending the instruction, the method further includesdisplaying the visual data. For example, the head-mounted display 140may receive the visual data from the host system, and may in turndisplay the visual data on the display 144. As an example, if the hostsystem receives information from the sensors 114 of the wearable device102 that the user has closed his fingers around a position correspondingto a coffee mug in the virtual environment and raised his hand, asimulated hand in a virtual-reality application picks up the virtualcoffee mug and lifts it to a corresponding height.

In conjunction with displaying the visual data, the wearable devicegenerates, by the two or more transducers, waves that constructivelyinterfere at a target location to create a haptic stimulation on a userof the wearable device (the user being the same user who is also wearingthe head-mounted display). Moreover, the haptic stimulation created onthe user corresponds to the visual data displayed by the host system.For example, using the coffee cup example from above, the hapticstimulation may prevent (or attempt to prevent) one or more of theuser's finger from curling past a certain point to simulate thesensation of touching a solid coffee mug.

To further illustrate the above, an exemplary embodiment is providedbelow.

In the particular example, the host 130 is a virtual (and/or augment)reality gaming device attached to a head-mounted display 140 (e.g., asshown in FIG. 1; AR system 1400, FIG. 14; VR 1500, FIG. 15). The host130 instructs the head-mounted display to display gaming data while theuser is playing the virtual-reality video game (e.g., video informationto be displayed by the head-mounted display). The gaming data, whendisplayed by the head-mounted display, depicts an insect crawling acrossthe wearer's hand in the virtual-reality video game. Concurrently, thehost may communicate an instruction to the wearable device, where theinstruction, when performed by the wearable device, causes the wearabledevice to generate waves by the two or more transducers that create ahaptic stimulation that mimics the insect displayed by the head-mounteddisplay 140 (i.e., the haptic stimulation coincides with the gaming datadisplayed by the head-mounted display 140). In this way, the user notonly experiences the insect visually, but also feels the insect crawlingon his or her hand in virtual and/or augment reality.

It is noted that multiple haptic stimulations can be created to followalong with the video information displayed by the head-mounted display140. For example, a first haptic stimulation may be created at a firsttime, a second haptic stimulation may be created at a second time, andso on. Moreover, if multiple wearable devices are in communication withthe host, then multiple haptic stimulations can be created at differentlocations on the user's body. For example, a first haptic stimulationmay be created at a first limb by a first wearable device, a secondhaptic stimulation may be created at a second limb by a second wearabledevice, and so on.

Embodiments of the instant disclosure may include or be implemented inconjunction with various types of artificial reality systems. Artificialreality may constitute a form of reality that has been altered byvirtual objects for presentation to a user. Such artificial reality mayinclude and/or represent VR, AR, MR, hybrid reality, or some combinationand/or variation of one or more of the same. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto a viewer). Additionally, in some embodiments, artificial reality mayalso be associated with applications, products, accessories, services,or some combination thereof, that are used to, e.g., create content inan artificial reality and/or are otherwise used in (e.g., to performactivities in) an artificial reality.

Artificial reality systems may be implemented in a variety of differentform factors and configurations. Some artificial reality systems may bedesigned to work without near-eye displays (NEDs), an example of whichis AR system 1300 in FIG. 13. Other artificial reality systems mayinclude an NED that also provides visibility into the real world (e.g.,AR system 1400 in FIG. 14) or that visually immerses a user in anartificial reality (e.g., VR system 1500 in FIG. 15). While someartificial reality devices may be self-contained systems, otherartificial reality devices may communicate and/or coordinate withexternal devices to provide an artificial reality experience to a user.Examples of such external devices include handheld controllers, mobiledevices, desktop computers, devices worn by a user (e.g., wearabledevice 102 a, wearable device 102 b, . . . wearable device 102 n),devices worn by one or more other users, and/or any other suitableexternal system.

FIGS. 13-15 provide additional examples of the devices used in thesystem 100. AR system 1300 in FIG. 13 generally represents a wearabledevice dimensioned to fit about a body part (e.g., a head) of a user.The AR system 1300 may include the functionality of the wearable device102, and may include additional functions. As shown, the AR system 1300includes a frame 1302 (e.g., band) and a camera assembly 1304 that iscoupled to frame 1302 and configured to gather information about a localenvironment by observing the local environment. The AR system 1300 mayalso include one or more transducers (e.g., instances of the transducers410, FIG. 4). In one example, the AR system 1300 includes outputtransducers 1308(A) and 1308(B) and input transducers 1310. Outputtransducers 1308(A) and 1308(B) may provide audio feedback, hapticfeedback, and/or content to a user, and input audio transducers maycapture audio (or other signals/waves) in a user's environment. As such,the transducers of the AR system 1300 may be configured to generatewaves for creating haptic stimulations, as discussed in detail above.

Thus, the AR system 1300 does not include a near-eye display (NED)positioned in front of a user's eyes. AR systems without NEDs may take avariety of forms, such as head bands, hats, hair bands, belts, watches,wrist bands, ankle bands, rings, neckbands, necklaces, chest bands,eyewear frames, and/or any other suitable type or form of apparatus.While the AR system 1300 may not include an NED, the AR system 1300 mayinclude other types of screens or visual feedback devices (e.g., adisplay screen integrated into a side of frame 1302).

The embodiments discussed in this disclosure may also be implemented inAR systems that include one or more NEDs. For example, as shown in FIG.14, the AR system 1400 may include an eyewear device 1402 with a frame1410 configured to hold a left display device 1415(A) and a rightdisplay device 1415(B) in front of a user's eyes. Display devices1415(A) and 1415(B) may act together or independently to present animage or series of images to a user. While the AR system 1400 includestwo displays, embodiments of this disclosure may be implemented in ARsystems with a single NED or more than two NEDs.

In some embodiments, the AR system 1400 may include one or more sensors,such as sensor 1440. Sensor 1440 may generate measurement signals inresponse to motion of AR system 1400 and may be located on substantiallyany portion of frame 1410. Sensor 1440 may include a position sensor, aninertial measurement unit (IMU), a depth camera assembly, or anycombination thereof. In some embodiments, the AR system 1400 may or maynot include sensor 1440 or may include more than one sensor. Inembodiments in which sensor 1440 includes an IMU, the IMU may generatecalibration data based on measurement signals from sensor 1440. Examplesof sensor 1440 may include, without limitation, accelerometers,gyroscopes, magnetometers, other suitable types of sensors that detectmotion, sensors used for error correction of the IMU, or somecombination thereof. Sensors are also discussed above with reference toFIG. 1 (e.g., sensors 145 of the head-mounted display 140).

The AR system 1400 may also include a microphone array with a pluralityof acoustic sensors 1420(A)-1420(J), referred to collectively asacoustic sensors 1420. Acoustic sensors 1420 may be transducers thatdetect air pressure variations induced by sound waves. Each acousticsensor 1420 may be configured to detect sound and convert the detectedsound into an electronic format (e.g., an analog or digital format). Themicrophone array in FIG. 14 may include, for example, ten acousticsensors: 1420(A) and 1420(B), which may be designed to be placed insidea corresponding ear of the user, acoustic sensors 1420(C), 1420(D),1420(E), 1420(F), 1420(G), and 1420(H), which may be positioned atvarious locations on frame 1410, and/or acoustic sensors 1420(I) and1420(J), which may be positioned on a corresponding neckband 1405. Insome embodiments, the neckband 1405 is an example of the computer system130.

The configuration of acoustic sensors 1420 of the microphone array mayvary. While the AR system 1400 is shown in FIG. 14 as having tenacoustic sensors 1420, the number of acoustic sensors 1420 may begreater or less than ten. In some embodiments, using higher numbers ofacoustic sensors 1420 may increase the amount of audio informationcollected and/or the sensitivity and accuracy of the audio information.In contrast, using a lower number of acoustic sensors 1420 may decreasethe computing power required by a controller 1450 to process thecollected audio information. In addition, the position of each acousticsensor 1420 of the microphone array may vary. For example, the positionof an acoustic sensor 1420 may include a defined position on the user, adefined coordinate on the frame 1410, an orientation associated witheach acoustic sensor, or some combination thereof.

Acoustic sensors 1420(A) and 1420(B) may be positioned on differentparts of the user's ear, such as behind the pinna or within the auricleor fossa. Or, there may be additional acoustic sensors on or surroundingthe ear in addition to acoustic sensors 1420 inside the ear canal.Having an acoustic sensor positioned next to an ear canal of a user mayenable the microphone array to collect information on how sounds arriveat the ear canal. By positioning at least two of acoustic sensors 1420on either side of a user's head (e.g., as binaural microphones), the ARdevice 1400 may simulate binaural hearing and capture a 3D stereo soundfield around about a user's head. In some embodiments, the acousticsensors 1420(A) and 1420(B) may be connected to the AR system 1400 via awired connection, and in other embodiments, the acoustic sensors 1420(A)and 1420(B) may be connected to the AR system 1400 via a wirelessconnection (e.g., a Bluetooth connection). In still other embodiments,acoustic sensors 1420(A) and 1420(B) may not be used at all inconjunction with the AR system 1400.

Acoustic sensors 1420 on frame 1410 may be positioned along the lengthof the temples, across the bridge, above or below display devices1415(A) and 1415(B), or some combination thereof. Acoustic sensors 1420may be oriented such that the microphone array is able to detect soundsin a wide range of directions surrounding the user wearing AR system1400. In some embodiments, an optimization process may be performedduring manufacturing of AR system 1400 to determine relative positioningof each acoustic sensor 1420 in the microphone array.

The AR system 1400 may further include or be connected to an externaldevice (e.g., a paired device), such as neckband 1405. As shown,neckband 1405 may be coupled to eyewear device 1402 via one or moreconnectors 1430. Connectors 1430 may be wired or wireless connectors andmay include electrical and/or non-electrical (e.g., structural)components. In some cases, eyewear device 1402 and neckband 1405 mayoperate independently without any wired or wireless connection betweenthem. While FIG. 14 illustrates the components of eyewear device 1402and neckband 1405 in example locations on eyewear device 1402 andneckband 1405, the components may be located elsewhere and/ordistributed differently on eyewear device 1402 and/or neckband 1405. Insome embodiments, the components of eyewear device 1402 and neckband1405 may be located on one or more additional peripheral devices pairedwith eyewear device 1402, neckband 1405, or some combination thereof.Furthermore, neckband 1405 generally represents any type or form ofpaired device. Thus, the following discussion of neckband 1405 may alsoapply to various other paired devices, such as smart watches, smartphones, wrist bands, other wearable devices, hand-held controllers,tablet computers, laptop computers, etc.

Pairing external devices, such as neckband 1405, with AR eyewear devicesmay enable the eyewear devices to achieve the form factor of a pair ofglasses while still providing sufficient battery and computation powerfor expanded capabilities. Some or all of the battery power,computational resources, and/or additional features of the AR system1400 may be provided by a paired device or shared between a paireddevice and an eyewear device, thus reducing the weight, heat profile,and form factor of the eyewear device overall while still retainingdesired functionality. For example, neckband 1405 may allow componentsthat would otherwise be included on an eyewear device to be included inneckband 1405 since users may tolerate a heavier weight load on theirshoulders than they would tolerate on their heads. Neckband 1405 mayalso have a larger surface area over which to diffuse and disperse heatto the ambient environment. Thus, neckband 1405 may allow for greaterbattery and computation capacity than might otherwise have been possibleon a stand-alone eyewear device. Since weight carried in neckband 1405may be less invasive to a user than weight carried in eyewear device1402, a user may tolerate wearing a lighter eyewear device and carryingor wearing the paired device for greater lengths of time than the userwould tolerate wearing a heavy standalone eyewear device, therebyenabling an artificial reality environment to be incorporated more fullyinto a user's day-to-day activities.

Neckband 1405 may be communicatively coupled with eyewear device 1402and/or to other devices. The other devices may provide certain functions(e.g., tracking, localizing, depth mapping, processing, storage, etc.)to the AR system 1400. In the embodiment of FIG. 14, neckband 1405 mayinclude two acoustic sensors (e.g., 1420(I) and 1420(J)) that are partof the microphone array (or potentially form their own microphonesubarray). Neckband 1405 may also include a controller 1425 and a powersource 1435.

Acoustic sensors 1420(I) and 1420(J) of neckband 1405 may be configuredto detect sound and convert the detected sound into an electronic format(analog or digital). In the embodiment of FIG. 14, acoustic sensors1420(I) and 1420(J) may be positioned on neckband 1405, therebyincreasing the distance between neckband acoustic sensors 1420(I) and1420(J) and other acoustic sensors 1420 positioned on eyewear device1402. In some cases, increasing the distance between acoustic sensors1420 of the microphone array may improve the accuracy of beamformingperformed via the microphone array. For example, if a sound is detectedby acoustic sensors 1420(C) and 1420(D) and the distance betweenacoustic sensors 1420(C) and 1420(D) is greater than, e.g., the distancebetween acoustic sensors 1420(D) and 1420(E), the determined sourcelocation of the detected sound may be more accurate than if the soundhad been detected by acoustic sensors 1420(D) and 1420(E).

Controller 1425 of neckband 1405 may process information generated bythe sensors on neckband 1405 and/or AR system 1400. For example,controller 1425 may process information from the microphone array thatdescribes sounds detected by the microphone array. For each detectedsound, controller 1425 may perform a direction of arrival (DOA)estimation to estimate a direction from which the detected sound arrivedat the microphone array. As the microphone array detects sounds,controller 1425 may populate an audio data set with the information. Inembodiments in which AR system 1400 includes an IMU, controller 1425 maycompute all inertial and spatial calculations from the IMU located oneyewear device 1402. Connector 1430 may convey information between ARsystem 1400 and neckband 1405 and between AR system 1400 and controller1425. The information may be in the form of optical data, electricaldata, wireless data, or any other transmittable data form. Moving theprocessing of information generated by AR system 1400 to neckband 1405may reduce weight and heat in eyewear device 1402, making it morecomfortable to a user.

Power source 1435 in neckband 1405 may provide power to eyewear device1402 and/or to neckband 1405. Power source 1435 may include, withoutlimitation, lithium-ion batteries, lithium-polymer batteries, primarylithium batteries, alkaline batteries, or any other form of powerstorage. In some cases, power source 1435 may be a wired power source.Including power source 1435 on neckband 1405 instead of on eyeweardevice 1402 may help better distribute the weight and heat generated bypower source 1435.

As noted, some artificial reality systems may, instead of blending anartificial reality with actual reality, substantially replace one ormore of a user's sensory perceptions of the real world with a virtualexperience. One example of this type of system is a head-worn displaysystem, such as VR system 1500 in FIG. 15, that mostly or completelycovers a user's field of view. VR system 1500 may include a front rigidbody 1502 and a band 1504 shaped to fit around a user's head. VR system1500 may also include output audio transducers 1506(A) and 1506(B).Furthermore, while not shown in FIG. 15, front rigid body 1502 mayinclude one or more electronic elements, including one or moreelectronic displays, one or more IMUs, one or more tracking emitters ordetectors, and/or any other suitable device or system for creating anartificial reality experience. Although not shown, the VR system 1500may include the computer system 130.

Artificial reality systems may include a variety of types of visualfeedback mechanisms. For example, display devices in AR system 1400and/or VR system 1500 may include one or more liquid-crystal displays(LCDs), light emitting diode (LED) displays, organic LED (OLED)displays, and/or any other suitable type of display screen. Artificialreality systems may include a single display screen for both eyes or mayprovide a display screen for each eye, which may allow for additionalflexibility for varifocal adjustments or for correcting a user'srefractive error. Some artificial reality systems may also includeoptical subsystems having one or more lenses (e.g., conventional concaveor convex lenses, Fresnel lenses, adjustable liquid lenses, etc.)through which a user may view a display screen.

In addition to or instead of using display screens, some artificialreality systems may include one or more projection systems. For example,display devices in AR system 1400 and/or VR system 1500 may includemicro-LED projectors that project light (using, e.g., a waveguide) intodisplay devices, such as clear combiner lenses that allow ambient lightto pass through. The display devices may refract the projected lighttoward a user's pupil and may enable a user to simultaneously view bothartificial reality content and the real world. Artificial realitysystems may also be configured with any other suitable type or form ofimage projection system.

Artificial reality systems may also include various types of computervision components and subsystems. For example, AR system 1300, AR system1400, and/or VR system 1500 may include one or more optical sensors suchas two-dimensional (2D) or three-dimensional (3D) cameras,time-of-flight depth sensors, single-beam or sweeping laserrangefinders, 3D LiDAR sensors, and/or any other suitable type or formof optical sensor. An artificial reality system may process data fromone or more of these sensors to identify a location of a user, to mapthe real world, to provide a user with context about real-worldsurroundings, and/or to perform a variety of other functions.

Artificial reality systems may also include one or more input and/oroutput audio transducers. In the examples shown in FIGS. 13 and 15,output audio transducers 1308(A), 1308(B), 1306(A), and 1506(B) mayinclude voice coil speakers, ribbon speakers, electrostatic speakers,piezoelectric speakers, bone conduction transducers, cartilageconduction transducers, and/or any other suitable type or form of audiotransducer. Similarly, input audio transducers 1310 may includecondenser microphones, dynamic microphones, ribbon microphones, and/orany other type or form of input transducer. In some embodiments, asingle transducer may be used for both audio input and audio output.

The artificial reality systems shown in FIGS. 13-15 may include tactile(i.e., haptic) feedback systems, which may be incorporated intoheadwear, gloves, body suits, handheld controllers, environmentaldevices (e.g., chairs, floormats, etc.), and/or any other type of deviceor system, such as the wearable devices 102 discussed herein.Additionally, in some embodiments, the haptic feedback systems may beincorporated with the artificial reality systems (e.g., the AR system1300 may include the wearable device 102 (FIG. 1). Haptic feedbacksystems may provide various types of cutaneous feedback, includingvibration, force, traction, texture, and/or temperature. Haptic feedbacksystems may also provide various types of kinesthetic feedback, such asmotion and compliance. Haptic feedback may be implemented using motors,piezoelectric actuators, fluidic systems, and/or a variety of othertypes of feedback mechanisms. Haptic feedback systems may be implementedindependent of other artificial reality devices, within other artificialreality devices, and/or in conjunction with other artificial realitydevices.

By providing haptic sensations, audible content, and/or visual content,artificial reality systems may create an entire virtual experience orenhance a user's real-world experience in a variety of contexts andenvironments. For instance, artificial reality systems may assist orextend a user's perception, memory, or cognition within a particularenvironment. Some systems may enhance a user's interactions with otherpeople in the real world or may enable more immersive interactions withother people in a virtual world. Artificial reality systems may also beused for educational purposes (e.g., for teaching or training inschools, hospitals, government organizations, military organizations,business enterprises, etc.), entertainment purposes (e.g., for playingvideo games, listening to music, watching video content, etc.), and/orfor accessibility purposes (e.g., as hearing aids, vision aids, etc.).The embodiments disclosed herein may enable or enhance a user'sartificial reality experience in one or more of these contexts andenvironments and/or in other contexts and environments.

Some AR systems may map a user's environment using techniques referredto as “simultaneous location and mapping” (SLAM). SLAM mapping andlocation identifying techniques may involve a variety of hardware andsoftware tools that can create or update a map of an environment whilesimultaneously keeping track of a device's or a user's location and/ororientation within the mapped environment. SLAM may use many differenttypes of sensors to create a map and determine a device's or a user'sposition within the map.

SLAM techniques may, for example, implement optical sensors to determinea device's or a user's location, position, or orientation. Radiosincluding WiFi, Bluetooth, global positioning system (GPS), cellular orother communication devices may also be used to determine a user'slocation relative to a radio transceiver or group of transceivers (e.g.,a WiFi router or group of GPS satellites). Acoustic sensors such asmicrophone arrays or 2D or 3D sonar sensors may also be used todetermine a user's location within an environment. AR and VR devices(such as systems 1300, 1400, and 1500) may incorporate any or all ofthese types of sensors to perform SLAM operations such as creating andcontinually updating maps of a device's or a user's current environment.In at least some of the embodiments described herein, SLAM datagenerated by these sensors may be referred to as “environmental data”and may indicate a device's or a user's current environment. This datamay be stored in a local or remote data store (e.g., a cloud data store)and may be provided to a user's AR/VR device on demand.

When the user is wearing an AR headset or VR headset in a givenenvironment, the user may be interacting with other users or otherelectronic devices that serve as audio sources. In some cases, it may bedesirable to determine where the audio sources are located relative tothe user and then present the audio sources to the user as if they werecoming from the location of the audio source. The process of determiningwhere the audio sources are located relative to the user may be referredto herein as “localization,” and the process of rendering playback ofthe audio source signal to appear as if it is coming from a specificdirection may be referred to herein as “spatialization.”

Localizing an audio source may be performed in a variety of differentways. In some cases, an AR or VR headset may initiate a DOA analysis todetermine the location of a sound source. The DOA analysis may includeanalyzing the intensity, spectra, and/or arrival time of each sound atthe AR/VR device to determine the direction from which the soundoriginated. In some cases, the DOA analysis may include any suitablealgorithm for analyzing the surrounding acoustic environment in whichthe artificial reality device is located.

For example, the DOA analysis may be designed to receive input signalsfrom a microphone and apply digital signal processing algorithms to theinput signals to estimate the direction of arrival. These algorithms mayinclude, for example, delay and sum algorithms where the input signal issampled, and the resulting weighted and delayed versions of the sampledsignal are averaged together to determine a direction of arrival. Aleast mean squared (LMS) algorithm may also be implemented to create anadaptive filter. This adaptive filter may then be used to identifydifferences in signal intensity, for example, or differences in time ofarrival. These differences may then be used to estimate the direction ofarrival. In another embodiment, the DOA may be determined by convertingthe input signals into the frequency domain and selecting specific binswithin the time-frequency (TF) domain to process. Each selected TF binmay be processed to determine whether that bin includes a portion of theaudio spectrum with a direct-path audio signal. Those bins having aportion of the direct-path signal may then be analyzed to identify theangle at which a microphone array received the direct-path audio signal.The determined angle may then be used to identify the direction ofarrival for the received input signal. Other algorithms not listed abovemay also be used alone or in combination with the above algorithms todetermine DOA.

In some embodiments, different users may perceive the source of a soundas coming from slightly different locations. This may be the result ofeach user having a unique head-related transfer function (HRTF), whichmay be dictated by a user's anatomy including ear canal length and thepositioning of the ear drum. The artificial reality device may providean alignment and orientation guide, which the user may follow tocustomize the sound signal presented to the user based on their uniqueHRTF. In some embodiments, an AR or VR device may implement one or moremicrophones to listen to sounds within the user's environment. The AR orVR device may use a variety of different array transfer functions (ATFs)(e.g., any of the DOA algorithms identified above) to estimate thedirection of arrival for the sounds. Once the direction of arrival hasbeen determined, the artificial reality device may play back sounds tothe user according to the user's unique HRTF. Accordingly, the DOAestimation generated using an ATF may be used to determine the directionfrom which the sounds are to be played from. The playback sounds may befurther refined based on how that specific user hears sounds accordingto the HRTF.

In addition to or as an alternative to performing a DOA estimation, anartificial reality device may perform localization based on informationreceived from other types of sensors. These sensors may include cameras,infrared radiation (IR) sensors, heat sensors, motion sensors, globalpositioning system (GPS) receivers, or in some cases, sensor that detecta user's eye movements. For example, an artificial reality device mayinclude an eye tracker or gaze detector that determines where a user islooking. Often, a user's eyes will look at the source of a sound, ifonly briefly. Such clues provided by the user's eyes may further aid indetermining the location of a sound source. Other sensors such ascameras, heat sensors, and IR sensors may also indicate the location ofa user, the location of an electronic device, or the location of anothersound source. Any or all of the above methods may be used individuallyor in combination to determine the location of a sound source and mayfurther be used to update the location of a sound source over time.

Some embodiments may implement the determined DOA to generate a morecustomized output audio signal for the user. For instance, an acoustictransfer function may characterize or define how a sound is receivedfrom a given location. More specifically, an acoustic transfer functionmay define the relationship between parameters of a sound at its sourcelocation and the parameters by which the sound signal is detected (e.g.,detected by a microphone array or detected by a user's ear). Anartificial reality device may include one or more acoustic sensors thatdetect sounds within range of the device. A controller of the artificialreality device may estimate a DOA for the detected sounds (using, e.g.,any of the methods identified above) and, based on the parameters of thedetected sounds, may generate an acoustic transfer function that isspecific to the location of the device. This customized acoustictransfer function may thus be used to generate a spatialized outputaudio signal where the sound is perceived as coming from a specificlocation.

Indeed, once the location of the sound source or sources is known, theartificial reality device may re-render (i.e., spatialize) the soundsignals to sound as if coming from the direction of that sound source.The artificial reality device may apply filters or other digital signalprocessing that alter the intensity, spectra, or arrival time of thesound signal. The digital signal processing may be applied in such a waythat the sound signal is perceived as originating from the determinedlocation. The artificial reality device may amplify or subdue certainfrequencies or change the time that the signal arrives at each ear. Insome cases, the artificial reality device may create an acoustictransfer function that is specific to the location of the device and thedetected direction of arrival of the sound signal. In some embodiments,the artificial reality device may re-render the source signal in astereo device or multi-speaker device (e.g., a surround sound device).In such cases, separate and distinct audio signals may be sent to eachspeaker. Each of these audio signals may be altered according to auser's HRTF and according to measurements of the user's location and thelocation of the sound source to sound as if they are coming from thedetermined location of the sound source. Accordingly, in this manner,the artificial reality device (or speakers associated with the device)may re-render an audio signal to sound as if originating from a specificlocation.

Although some of various drawings illustrate a number of logical stagesin a particular order, stages which are not order dependent may bereordered and other stages may be combined or broken out. While somereordering or other groupings are specifically mentioned, others will beobvious to those of ordinary skill in the art, so the ordering andgroupings presented herein are not an exhaustive list of alternatives.Moreover, it should be recognized that the stages could be implementedin hardware, firmware, software or any combination thereof.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific embodiments. However, theillustrative discussions above are not intended to be exhaustive or tolimit the scope of the claims to the precise forms disclosed. Manymodifications and variations are possible in view of the aboveteachings. The embodiments were chosen in order to best explain theprinciples underlying the claims and their practical applications, tothereby enable others skilled in the art to best use the embodimentswith various modifications as are suited to the particular usescontemplated.

It is noted that the embodiments disclosed herein can also be combinedwith any of the embodiments described in U.S. Provisional ApplicationNo. 62/636,699, filed Feb. 28, 2018, entitled “Methods, Devices, andSystems for Creating Haptic Stimulations and Tracking Motion of a User;”U.S. Provisional Application No. 62/647,559, filed Mar. 23, 2018,entitled “Methods, Devices, and Systems for Determining Contact On aUser of a Virtual Reality and/or Augmented Reality Device;” and U.S.Provisional Application No. 62/647,560, filed Mar. 23, 2018, entitled“Methods, Devices, and Systems for Projecting an Image Onto a User andDetecting Touch Gestures.”

It is also noted that the embodiments disclosed herein can also becombined with any of the embodiments described in U.S. Utility patentapplication Ser. No. 16/241,890 entitled “Methods, Devices, and Systemsfor Determining Contact On a User of a Virtual Reality and/or AugmentedReality Device,” filed Jan. 7, 2019, U.S. Utility patent applicationSer. No. 16/241,893, entitled “Methods, Devices, and Systems forDisplaying a User Interface on a User and Detecting Touch Gestures,”filed Jan. 7, 2019, and U.S. Utility patent application Ser. No.16/241,871, entitled “Methods, Devices, and Systems for Creating HapticStimulations and Tracking Motion of a User,” filed Jan. 7, 2019, each ofwhich is incorporated by reference herein in its entirety.

What is claimed is:
 1. A method, comprising: at a wearable devicecomprising a plurality of transducers that can each generate one or morewaves that propagate away from the wearable device through a medium:selecting two or more transducers of the plurality of transducers;selecting values for characteristics of waves to be generated by the twoor more transducers based, at least in part, on a known impedance of themedium; and activating the two or more transducers, producing waveshaving the selected values, including transmitting the waves into awrist of a user in a first direction, wherein the waves propagatethrough the user's body away from the wrist in a second direction andconstructively interfere at a target location to create a hapticstimulation on the user, and the first direction is substantiallyperpendicular to the second direction.
 2. The method of claim 1, whereinactivating the two or more transducers comprises: activating a firsttransducer of the two or more transducers at a first time; andactivating a second transducer of the two or more transducers at asecond time after the first time.
 3. The method of claim 1, whereinactivating the two or more transducers comprises activating the two ormore transducers simultaneously.
 4. The method of claim 1, furthercomprising, at the wearable device: receiving an instruction from a hostin communication with the wearable device, wherein activating the two ormore transducers is performed in response to receiving the instructionfrom the host.
 5. The method of claim 4, wherein the instructionreceived from the host identifies the target location.
 6. The method ofclaim 4, wherein: the wearable device further comprises a communicationradio in wireless communication with the host; and the communicationradio receives the instruction from the host.
 7. The method of claim 1,wherein: the wearable device further comprises a controller incommunication with the plurality of transducers; and the controllerperforms the activating and the selecting.
 8. The method of claim 1,wherein: the wearable device is a first wearable device; the selectedvalues are first selected values; the plurality of transducers is afirst plurality of transducers; the haptic stimulation created by thewaves generated by the two or more transducers is a first hapticstimulation; and the method further comprises, at a second wearabledevice comprising a second plurality of transducers that can eachgenerate one or more waves that propagate away from the second wearabledevice through the medium: activating two or more transducers of thesecond plurality of transducers; selecting second values forcharacteristics of waves generated by the two or more transducers of thesecond plurality of transducers based, at least in part, on the knownimpedance of the medium; and generating, by the two or more transducersof the second plurality of transducers, waves that constructivelyinterfere at a different target location to create a second hapticstimulation on the user, the waves having the second selected values. 9.The method of claim 8, wherein: the medium associated with the firstwearable device is a first medium; and the medium associated with thesecond wearable device is a second medium having a different knownimpedance from the known impedance of the first medium.
 10. The methodof claim 9, wherein the second selected values differ from the firstselected values based on impedance differences between the first andsecond media.
 11. The method of claim 1, wherein the target location isseparated from the wearable device by a distance.
 12. The method ofclaim 1, wherein: the wearable device further comprises a band to besecured around a wrist of the user; and each of the plurality oftransducers is coupled to the band.
 13. The method of claim 12, whereintransducers of the plurality of transducers are radially spaced along aperimeter of the band.
 14. The method of claim 13, wherein the two ormore transducers are separated from one another by at least one othertransducer.
 15. The method of claim 13, wherein the two or moretransducers are adjacent to one another on the wearable device.
 16. Themethod of claim 13, wherein transducers of the plurality of transducersare spaced equidistant from one another on the wearable device.
 17. Themethod of claim 1, wherein: the plurality of transducers is a firstplurality of transducers, and the wearable device further comprises asecond plurality of transducers.
 18. A wearable device, comprising: aplurality of transducers, each transducer being configured to generateone or more waves that propagate away from the wearable device through amedium; one or more processors; and memory storing one or more programs,which when executed by the one or more processors cause the wearabledevice to: select two or more transducers of the plurality oftransducers; select values for characteristics of waves to be generatedby the two or more transducers based, at least in part, on a knownimpedance of the medium; and activate the two or more transducers,producing waves having the selected values, including transmitting thewaves into a wrist of a user in a first direction, wherein the wavespropagate through the user's body away from the wrist in a seconddirection and constructively interfere at a target location to create ahaptic stimulation on the user, and the first direction is substantiallyperpendicular to the second direction.
 19. A non-transitorycomputer-readable storage medium storing one or more programs configuredfor execution by one or more processors of a wearable device having aplurality of transducers, each transducer being configured to generateone or more waves that propagate away from the wearable device through amedium, the one or more programs including instructions, which whenexecuted by the one or more processors cause the wearable device to:select two or more transducers of the plurality of transducers; selectvalues for characteristics of waves to be generated by the two or moretransducers based, at least in part, on a known impedance of the medium;and activate the two or more transducers, producing waves having theselected values, including transmitting the waves into a wrist of a userin a first direction, wherein the waves propagate through the user'sbody away from the wrist in a second direction and that constructivelyinterfere at a target location to create a haptic stimulation on theuser, and the first direction is substantially perpendicular to thesecond direction.